name: jadarian crump 5th
properties of water and ph
1. write the chemical equation for water, and draw a stick model of a water molecule. show polarity by label positive and negatively charged regions of the molecule.
3. what kind of bond holds the hydrogen to the oxygen in one water molecule?
4. what kind of bonds can hold two separate water molecules together?
5. what is a polar molecule?
6. the polarity of water allows it to ______________ most substances. because of this it is referred to as the ____________________ ____________________.
7. water molecules stick to other water molecules. this property is called ______________.
8. water molecules stick to other water molecules. this property is called ______________.
9. why does ice float on water?
10. why is it important that water resists temperature changes?
critical reading: ph
when some substances dissolve in water they break up into ions. a compound that releases a hydrogen ion (a proton) when it dissolves in water is an acid. bases are compounds that remove, or accept, hydrogen ions. a solution’s acidity, or its hydrogen ion concentration, is measured on the ph scale. an acid has a low ph (ph below 7) and a high hydrogen ion concentration. a base has a high ph (ph above 7) and a low hydrogen ion concentration. organisms must maintain a stable ph. even a small change in ph can disrupt many biological processes.
11. describe what the ph of a substance is measuring.
12. draw the ph scale and label acid, neutral, and base.
13. what has more hydrogen ions, acids or bases?

Question

Accepted Answer

### Question 3
# Brief Explanations:
In a water molecule ($H_2O$), the bond between hydrogen and oxygen within one molecule is a covalent bond. Specifically, it is a polar covalent bond because oxygen is more electronegative than hydrogen, causing an unequal sharing of electrons.
# Answer:
The bond that holds hydrogen to oxygen in one water molecule is a polar covalent bond.

### Question 4
# Brief Explanations:
Two separate water molecules are held together by hydrogen bonds. The slightly positive hydrogen atom of one water molecule is attracted to the slightly negative oxygen atom of another water molecule, forming these intermolecular hydrogen bonds.
# Answer:
The bonds that can hold two separate water molecules together are hydrogen bonds.

### Question 5
# Brief Explanations:
A polar molecule is a molecule in which there is an unequal distribution of electron density, resulting in a molecule with a partial positive charge on one end and a partial negative charge on the other end. This occurs when there is a significant difference in electronegativity between the atoms in the molecule, leading to a dipole moment (a separation of charge). For example, water ($H_2O$) is a polar molecule because the oxygen atom is more electronegative than the hydrogen atoms, pulling the shared electrons closer to itself and creating a partial negative charge on the oxygen and partial positive charges on the hydrogens.
# Answer:
A polar molecule is a molecule with an unequal distribution of electron density, having a partial positive charge on one part and a partial negative charge on another part (due to differences in electronegativity between atoms, creating a dipole moment).

### Question 6
# Brief Explanations:
The polarity of water allows it to dissolve most substances. Because of this ability to dissolve many solutes (especially polar and ionic substances), it is referred to as the universal solvent. The polar nature of water molecules (with partial positive and negative charges) allows them to interact with and surround other polar or charged particles, pulling them apart and dispersing them in the water.
# Answer:
The polarity of water allows it to $\boldsymbol{\text{dissolve}}$ most substances. Because of this it is referred to as the $\boldsymbol{\text{universal solvent}}$.

### Question 7 (and Question 8, which appears to be a duplicate)
# Brief Explanations:
The property where water molecules stick to other water molecules is called cohesion. Cohesion is due to the hydrogen bonds between water molecules. These bonds cause the water molecules to be attracted to one another, leading to phenomena like surface tension (where the surface of water can support small objects due to the cohesive forces between the water molecules at the surface).
# Answer:
Water molecules stick to other water molecules. This property is called $\boldsymbol{\text{cohesion}}$.

### Question 9
# Brief Explanations:
Ice floats on water because the density of ice is less than the density of liquid water. When water freezes into ice, the water molecules form a crystalline structure (a hexagonal lattice) due to hydrogen bonding. In this structure, the molecules are spaced further apart from each other compared to the more random arrangement of molecules in liquid water. Since density is mass per unit volume, and the same mass of water takes up more volume in the solid (ice) state, the density of ice ($\approx 0.92\space g/cm^3$) is less than the density of liquid water ($\approx 1.0\space g/cm^3$). An object with a lower density than the fluid it is in will float.
# Answer:
Ice floats on water because the density of ice is less than the density of liquid water. When water freezes, it forms a crystalline structure (due to hydrogen bonding) with molecules spaced further apart, resulting in a lower density for ice compared to liquid water.

### Question 10
# Brief Explanations:
It is important that water resists temperature changes (has a high specific heat capacity) because this property helps to stabilize temperatures in the environment and in organisms. In the environment, large bodies of water (like oceans, lakes) can absorb and release heat without undergoing drastic temperature changes, which moderates the climate of nearby land areas. In organisms, water (which makes up a large portion of many organisms) can help regulate body temperature. For example, sweating in humans uses the heat of vaporization of water (related to its ability to resist temperature changes) to cool the body, and the high specific heat of water in cells helps maintain a relatively constant internal temperature, which is essential for the proper functioning of enzymes and other biological processes that are sensitive to temperature.
# Answer:
Water resisting temperature changes (high specific heat) is important because it stabilizes environmental temperatures (moderating climate) and helps organisms regulate body temperature, maintaining conditions for vital biological processes (e.g., enzyme function) that are temperature - sensitive.

### Question 11
# Brief Explanations:
The pH of a substance is measuring the acidity (or alkalinity) of a solution, specifically the hydrogen ion concentration ($[H^+]$) in the solution. Mathematically, $pH = -\log_{10}[H^+]$, where $[H^+]$ is the molar concentration of hydrogen ions. A low pH (below 7) indicates a high hydrogen ion concentration (an acidic solution), while a high pH (above 7) indicates a low hydrogen ion concentration (a basic or alkaline solution), and a pH of 7 is neutral (equal concentrations of $H^+$ and $OH^-$ ions in pure water).
# Answer:
The pH of a substance measures the hydrogen ion concentration ($[H^+]$) in a solution (or the acidity/alkalinity of the solution), with $pH = -\log_{10}[H^+]$. It indicates whether a solution is acidic (low pH, high $[H^+]$), neutral (pH = 7), or basic (high pH, low $[H^+]$).

### Question 12
# Brief Explanations:
To draw the pH scale:
1. Draw a horizontal line.
2. Label the left - hand end as "Acid" and the right - hand end as "Base".
3. Mark the center of the line as "Neutral" (pH = 7).
4. Mark values from 0 to 14 along the line, with 0 being the most acidic, 14 being the most basic, and 7 in the middle (neutral, like pure water). For example:
| pH Range | Classification | Example |
|----|----|----|
| 0 - 6.9 | Acidic | Lemon juice (pH $\approx 2$) |
| 7 | Neutral | Pure water |
| 7.1 - 14 | Basic | Baking soda solution (pH $\approx 9$) |

# Answer:
To draw the pH scale:
- Draw a horizontal line.
- Label the left as "Acid" (pH 0 - 6.9), the middle as "Neutral" (pH = 7), and the right as "Base" (pH 7.1 - 14).
- Mark pH values 0 (most acidic) to 14 (most basic) along the line, with 7 at the center.

### Question 13
# Brief Explanations:
Acids have more hydrogen ions than bases. By definition, an acid is a compound that releases (or donates) hydrogen ions ($H^+$) when it dissolves in water, while a base removes (or accepts) hydrogen ions. So, in an acidic solution, the concentration of $H^+$ ions is high (leading to a low pH), and in a basic solution, the concentration of $H^+$ ions is low (leading to a high pH).
# Answer:
Acids have more hydrogen ions than bases.

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